Flashcards in Lesson 3 Review Deck (18)
What is Refrigeration?
The process of transferring heat energy from the area it is not wanted to an area it won't make a difference.
SEER is the measure of a heat pumps____. It is expressed in___
Cooling efficiency; Btu/Watt
The typical compression ratio for a heat pump operating in cooling mode is approximately?
What is the coefficient of performance (COP) of a heat pump?
How much heat the heat pump is producing compared to and electric furnace using the same amount of electricity.
A heat pump thermostat is set so that there will be a deadband range of about ___ deg. F between the heating & cooling cycles, A closer setting might result in ___
2 to 4 degrees F ; frequent cycling
A typical reversing valve cylinder with 3 tubes on one side and a single tube on the other side. The center tube of the three is always the compressor ___ connection. The single tube on the opposite side of the cylinder is always the compressor ___ connection.
At what liquid line temperature does a temperature-activated defrost control typically terminate the defrost cycle?
50 to 65 deg. F
At what head pressure does a pressure-activated defrost control typically terminate the defrost cycle?
250 to 300 psig
Why does a heat pump require three-function control?
because a H.P. provides 3 functions: heating, cooling and defrosting the outdoor coil of ice build up
What is meant by excessive supplemental heat?
More heat than would be required to neutralize the cooling effect that occurs during the defrost cycle
What is the "critical point" of refrigerant?
The maximum saturation condition at which evaporation and condensation may occur
The physical properties of a refrigerant may be represented as a curve on a pressure-enthalpy diagram. Plots points that fall outside and to the right of curve indicate that refrigerant is a ___. Plot points that fall outside and to the left indicate that the refrigerant is an ___. Plot points that fall inside the curve itself indicate that the refrigerant is a ___.
Superheated vapor, subcooled liquid, mixture of saturated liquid and vapor
One of the most important principles of refrigeration is that an increase in pressure on a liquid results in an ___ in the liquids boiling temperature.
In the cooling mode, which coil (indoor or outdoor) of a heat pump system functions as a condenser? Which coil during the heating mode?
In the cooling mode, the outdoor coil functions as the condenser. In the heating mode, the indoor coil functions as the condenser.
What is meant by referring to a vapor compression system as a "closed" system?
The term "closed" means the system continually repeats itself without depleting the refrigerant contained within it.
Why are suction-line accumulators and crankcase heaters often required to protect heat pump compressors?
liquid refrigerant can build up in the crankcase during the off-cycle which causes poor lubrication on start up and increases bearing wear.
Why is the indoor air volume required for heat pump operation greater than the volume required for cooling only applications?
To ensure adequate condensing of the refrigerant during the heating mode.